Field of the Invention
The present invention relates to a wireless communication system, and more particularly, to a method for preventing a peer discovery signal collision which may occur in a device-to-device (D2D) communication system, and a wireless device using the method.
Related Art
In a typical cellular communication system, a user equipment always exchanges data with a base station. Therefore, data transmission between user equipments requires a procedure in which data is first delivered from one user equipment to the base station and then is delivered from the base station to another user equipment. In this case, a channel for transmitting data from the user equipment to the base station is called an uplink channel, and a channel for transmitting data from the base station to the user equipment is called a downlink channel. As such, in the data communication between the user equipments in the typical cellular communication system, both of the downlink channel and the downlink channel must be used, and a resource must be allocated to each channel. For this, the base station identifies user equipments within a cell of the base station, forms a data transport channel with the user equipment, and allocates a resource to the data transport channel.
Meanwhile, a device-to-device (D2D) communication system performs communication by directly transmitting data between wireless devices in the absence of the base station. Therefore, D2D communication is also called direct communication. Since a single transport channel is formed between the wireless devices, there is an advantage in that data can be transmitted between the wireless devices by allocating resources only one time. However, since the base station does not exist which forms the transport channel between the wireless devices and allocates the resources to the data transport channel, there is a need for a method of replacing the role of the base station.